The invention relates to a resin-sand mixer for preparing a mixture of sand and resin. A known mixer comprises walls which form an inlet for the sand, an annular gap for the sand following the inlet. The gap is followed by an axially symmetrical mixing chamber and an outlet for the mixture. The mixing chamber has provided therein a supply arrangement with pipes for the separate components of the resin and has a rotatable dished member arranged beneath the pipes. Two solids of revolution arranged coaxially one above the other are provided between the mixing chamber and the outlet, between which solids is left an annular interstice for the mixture. The lower of the solids of revolution defines the mixing chamber in a downward axial direction and is rotatable.
Mixers of this type are used in foundries for the preparation of the resin moulding sand. With the prior mixers, the components of the resin are distributed in the sand by spraying. Compressed air serves, for example, for this purpose in one known mixer, by means of which air the components of the resin are atomised and thus dispersed in the sand.
With another known mixer, the components of the resin are guided into a bowl-like rotor device which can be rotated at very high speed by means of an additional motor, the resin being sprayed out of the said bowl by means of centrifugal force through radial openings which are provided.
In both cases, the components of the resin are atomised, as a result of which is a certain danger of explosion of the air-mist mixture as thus formed, due to self-ignition.